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Java example source code file (arena.hpp)

This example Java source code file (arena.hpp) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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Java - Java tags/keywords

afree, amalloc, arealloc, arena, cheapobj, chop, chunk, first, get, handlemark, high, resourcemark, share_vm_adlc_arena_hpp, size

The arena.hpp Java example source code

/*
 * Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#ifndef SHARE_VM_ADLC_ARENA_HPP
#define SHARE_VM_ADLC_ARENA_HPP

// All classes in the virtual machine must be subclassed
// by one of the following allocation classes:
//
//
// For objects allocated in the C-heap (managed by: free & malloc).
// - CHeapObj
//
//
// For embedded objects.
// - ValueObj
//
// For classes used as name spaces.
// - AllStatic
//

class CHeapObj {
 public:
  void* operator new(size_t size) throw();
  void  operator delete(void* p);
  void* new_array(size_t size);
};


// Base class for objects used as value objects.
// Calling new or delete will result in fatal error.

class ValueObj {
 public:
  void* operator new(size_t size) throw();
  void operator delete(void* p);
};

// Base class for classes that constitute name spaces.

class AllStatic {
 public:
  void* operator new(size_t size) throw();
  void operator delete(void* p);
};


//------------------------------Chunk------------------------------------------
// Linked list of raw memory chunks
class Chunk: public CHeapObj {
 public:
  void* operator new(size_t size, size_t length) throw();
  void  operator delete(void* p, size_t length);
  Chunk(size_t length);

  enum {
      init_size =  1*1024,      // Size of first chunk
      size      = 32*1024       // Default size of an Arena chunk (following the first)
  };
  Chunk*       _next;           // Next Chunk in list
  size_t       _len;            // Size of this Chunk

  void chop();                  // Chop this chunk
  void next_chop();             // Chop next chunk

  // Boundaries of data area (possibly unused)
  char* bottom() const { return ((char*) this) + sizeof(Chunk);  }
  char* top()    const { return bottom() + _len; }
};


//------------------------------Arena------------------------------------------
// Fast allocation of memory
class Arena: public CHeapObj {
protected:
  friend class ResourceMark;
  friend class HandleMark;
  friend class NoHandleMark;
  Chunk *_first;                // First chunk
  Chunk *_chunk;                // current chunk
  char *_hwm, *_max;            // High water mark and max in current chunk
  void* grow(size_t x);         // Get a new Chunk of at least size x
  size_t _size_in_bytes;          // Size of arena (used for memory usage tracing)
public:
  Arena();
  Arena(size_t init_size);
  Arena(Arena *old);
  ~Arena()                      { _first->chop(); }
  char* hwm() const             { return _hwm; }

  // Fast allocate in the arena.  Common case is: pointer test + increment.
  void* Amalloc(size_t x) {
#ifdef _LP64
    x = (x + (8-1)) & ((unsigned)(-8));
#else
    x = (x + (4-1)) & ((unsigned)(-4));
#endif
    if (_hwm + x > _max) {
      return grow(x);
    } else {
      char *old = _hwm;
      _hwm += x;
      return old;
    }
  }
  // Further assume size is padded out to words
  // Warning:  in LP64, Amalloc_4 is really Amalloc_8
  void *Amalloc_4(size_t x) {
    assert( (x&(sizeof(char*)-1)) == 0, "misaligned size" );
    if (_hwm + x > _max) {
      return grow(x);
    } else {
      char *old = _hwm;
      _hwm += x;
      return old;
    }
  }

  // Fast delete in area.  Common case is: NOP (except for storage reclaimed)
  void Afree(void *ptr, size_t size) {
    if (((char*)ptr) + size == _hwm) _hwm = (char*)ptr;
  }

  void *Acalloc( size_t items, size_t x );
  void *Arealloc( void *old_ptr, size_t old_size, size_t new_size );

  // Reset this Arena to empty, and return this Arenas guts in a new Arena.
  Arena *reset(void);

  // Determine if pointer belongs to this Arena or not.
  bool contains( const void *ptr ) const;

  // Total of all chunks in use (not thread-safe)
  size_t used() const;

  // Total # of bytes used
  size_t size_in_bytes() const         {  return _size_in_bytes; }
  void   set_size_in_bytes(size_t size)  { _size_in_bytes = size;   }
};

#endif // SHARE_VM_ADLC_ARENA_HPP

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